Planck Mission: Space Probe Peers Into Dark Cosmos

Jun 10, 2010 By Carl Marziali

An artist's impression depicts the Planck telescope against a background image of the large-scale structure in the Milky Way. Photo copyright European Space Agency.

(PhysOrg.com) -- Imagine watching the birth of the universe -- the Big Bang -- from the outside. What would you have seen?

At that moment and for the next 380,000 years, a Big Nothing, as photons and particles clung to each other in a high-energy dance that kept any light from escaping.

USC College’s Elena Pierpaoli and 200 other physicists are trying to find out what went on during those dark days with the Planck mission — the most advanced space-based telescope designed to study the early universe.

Named after the founder of quantum theory and launched last year by the European Space Agency, Planck in coming years will map the weak background radiation pervading the universe with far greater accuracy than two previous missions.

“The [cosmic background radiation] is a gold mine to test various theories regarding the early universe,” Pierpaoli said. “It’s a section of the history of the cosmos that we don’t know much about and it’s incredibly important.”

Planck also could become the first telescope to prove the existence of gravity waves: ripples in space-time caused by the extreme phenomena of the birthing universe. If they exist, gravity waves would have left a unique signature on the cosmic background radiation (CMB).

The discovery of gravity waves would lift the darkness and help cosmologists — physicists who study the origins of the cosmos — to decide between several theories of the early universe.

While the discovery of gravitational waves may not occur even with Planck, there is no doubt about the probe’s main capability: mapping the cosmic background radiation with unparalleled accuracy.

The radiation was the first light released after the decoupling of photons and particles. So while it is not as old as gravity waves, it can still provide new information about the cosmos. And it may carry the imprint of a very fast expansion, known as inflation, theorized to have occurred a millionth of a second after the Big Bang.

As the graduate student of one of the mission’s first proponents in the early 1990s, Pierpaoli was grandfathered into the worldwide community behind the telescope. She joined USC College in 2006, becoming associate professor of physics the following year.

Pierpaoli and her postdoctoral researcher Loris Colombo, also on the Planck team, hope to use the data to sharpen estimates of some fundamental numbers: the total mass of the universe; the amount of mysterious “dark energy” driving the expansion of the universe; the speed of expansion; and several numbers relating to inflation.

Planck should improve the accuracy of existing estimates by three to four times, Pierpaoli said. That in turn could be used to confirm or rule out competing theories of the universe.

Pierpaoli and Colombo also hope to find signatures in the cosmic background radiation from the period after decoupling, when matter started forming into atoms and emitting radiation.

Finally, Planck is expected to provide valuable data on galaxy clusters, the largest objects bound by gravity in the known universe.

“There’s much more science contained in the Planck measurements than just the CMB data. By observing the entire sky at nine different frequencies, ranging from the radio to the infrared, we’ll be able to learn more about distant galaxies, other galaxy clusters and our own galaxy,” Pierpaoli said while the Planck mission was in the planning stage.

Galaxy clusters are supposed to be spread over the cosmos more or less randomly. If unexpected variations were to turn up, they might indicate that something was not quite random during inflation — the way an unusual scatter pattern from shotgun pellets might indicate a burr in the barrel.

Pierpaoli and graduate student Thad Szabo are about to publish the newest and biggest survey of galaxy clusters as seen in the visible light in the Sloan Digital Sky Survey, containing 72,000 objects — five times more than previously surveyed.

New data expected from Planck will further improve scientists’ understanding of clusters, along with the other phenomena related to the birth of the universe.
It’s not as good as a front row seat to the Big Bang, but it’s a start.

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User comments : 20

What about looking before the Big Bang time ? How about that, but it may indeed be just nothing as per theory, but don't forget that the observations shape theory, not the other way around. I'm more curious what is hidden from us in the real-time universe, where we only see the past.

The joke here is that the CMB moves at the speed of light, yet if as the theory states, the CMB is the first light in the universe, then that means "somehow" we got ahead of it, and it has now taken supposedly 13 billion years to catch back up to us...

@QC: No, the CMB occured in the early stage of the universe, and was "stretched" along as the space expanded. That was the winning point for the Big Bang theory over the Steady-State theory. The CMB is a left over temperature of the Big Bang itself.

Imagine watching the birth of the universe -- the Big Bang -- from the outside.

Erm.... I'd just like to point out that according to currently dominant cosmology, there is no "outside". The entirety of our infinite space was initially compressed at every point, then inflated at every point, then continued to expand at every point while being seeded with matter and energy at every point. Anywhere in space, you'd observe pretty much the same thing we're observing from earth. No location is privileged, and there's no border or boundary in any direction, beyond which you might find something different.

So to reiterate, within our 3 spatial dimensions, there is NO "outside"... at least until some empirical evidence arises to disprove that simplifying assumption.

Now, if there are extra dimensions currently inaccessible to us, then they might be "outside" our 3D "membrane". But can anything exist there, much less "see" anything: that's a different question entirely...

@PEThanks. Disappointing, but not entirely unexpected- that is, if the inhabitants of the naked scientists.com are to be trusted with the calculations. A not=negligible amount, but far short of the nnecessary amount.

Also- I'm still wondering about a phase or change- -of-state model to explain the unobservsd part.

Just contemplating observing the universe from outside. Even is we presumed three dimensions expanded well beyond universe boundary we would not be able to observe anything of our known universe as it apparently is apparently expanding at greater then C speed.

If we were just outside maximum size of universe and did not continue to move back then we would end up inside universe pretty quick.

The radiation was the first light released after the decoupling of photons and particles.

In accord with "Quantum" I do wish they would state this as "The radiation is thought to be...".

@PinkElephant

The entirety of our infinite space was initially compressed at every point, then inflated at every point, then continued to expand at every point while being seeded with matter and energy at every point. Anywhere in space, you'd observe pretty much the same thing we're observing from earth

I'm puzzled by this statement since we can clearly see irregularities in the CMB.

We can also see that the universe has structure - clusters and super clusters and filaments and streets. With lots of un-even empty spaces in between.

So how can it be stated that it looks the same from any point to another?

Furthermore if it is so homogeneous, why are all currently observed celestial bodies UNIQUE?

The joke here is that the CMB moves at the speed of light, yet if as the theory states, the CMB is the first light in the universe, then that means "somehow" we got ahead of it, and it has now taken supposedly 13 billion years to catch back up to us...

No. Remember space isn't being created, it's simply expanding. The Big Bang is the beginning of inflation everywhere in the universe. The CMB hasn't moved, it has stretched, hence why it has a lower frequency than light. The CMB doesn't travel from place to place, it travels with each place.

I'm puzzled by this statement since we can clearly see irregularities in the CMB.

Irregularities are to be expected, since inflation is thought to have magnified space so much that quantum-scale fluctuations (i.e. what was initially "quantum foam") were expanded into cosmic-scale structure. Indeed, the theory is that those initial quantum fluctuations are what "seeded" the formation of galaxies, galaxy clusters, super-clusters, and present-day walls and voids.

So how can it be stated that it looks the same from any point to another?

What is meant by such a statement, is that at any point in infinite space, the universe is self-similar, like a fractal. Same kinds of galaxies, superclusters, walls and voids, etc. Same abundances of elements. Same laws of physics, same energetics, same gravitational features, etc.

CMB is just a bunch of photons, permeating the entire universe like a sort of photonic "fog". Each individual photon moves at lightspeed, but overall the photon directions are random. The CMB photons we see with our telescopes (or more accurately, with our antennas) today, happen to have been traveling toward us through space from other points in space, ever since the decoupling event (i.e. for ~14 billion years, give or take half a billion.)

Initially, these were ultra-high-energy gamma ray photons flooding every unit volume of space like a torrent of super-intense laser light. But as they propagate through space in every which direction since then, the space continues to expand within them and between them, thereby stretching their wavelengths until today they're mere microwaves, and increasing the space between them, so that their density in space today is very low compared to what it used to be.